1. Field of the Invention
The present invention relates to a pneumatic tire which is to be mainly attached to a car.
2. Description of the Related Art
A radial tire for high speed straight running comprises a band between a tread and a belt. The band includes a band cord wound in a circumferential direction. The band cord restrains the belt. Lifting of the belt which is caused by a centrifugal force in the high speed straight running is controlled by the band cord. US2005/0205189 (JP-A No. 2005-263137) has disclosed a pneumatic tire which is excellent in a silence and a ride comfort. In the tire, the band includes a side portion positioned in the vicinity of an outer end of the belt and a center portion positioned on a center in an axial direction. The side portion includes a band cord having a high modulus. The center portion includes a band cord having a low modulus.
The band for covering a whole region of the belt fully restrains the vicinity of a center of the belt. On the other hand, in the band, the control of a restraining force in the vicinity of an outer end of the belt is not relatively sufficient. In the band, the control of the lifting in the vicinity of the outer end is not relatively sufficient. A road noise cannot be fully reduced by the relatively insufficient restraining force.
By using a cord having a high modulus for the band, the vicinity of the outer end of the belt can be sufficiently restrained. By the band, rigidity of the tire is excessively increased. The excessive rigidity hinders the ride comfort of the tire. The band causes a great outside noise. If the modulus of the cord is excessively high, a handling stability is also deteriorated.
When the outer end of the band and that of the belt overlap each other in an axial direction, a step is formed. In some cases in which a great step is formed, air remains in the tire at a vulcanizing step. In these cases, an air remaining defect is generated in the tire.
There are some tires using a band including a band cord having a high modulus. In the tire, an outside diameter of the band is not sufficiently enlarged at the vulcanizing step. For this reason, a nonuniform deformation is caused over a green tire in some cases. In the tire, a uniformity is deteriorated.
The band cord is wound spirally in a circumferential direction and is slightly inclined with respect to the circumferential direction. At the outer end of the band restraining the belt, therefore, the rigidity in the circumferential direction of the band is partially changed. In a tire in which the outer end of the band is provided on the outside in the axial direction of the outer end of the belt, the change of the rigidity hinders the uniformity of the tire in some cases. In a tire using a band cord having a high modulus in a band, particularly, the uniformity is remarkably hindered due to the change of the rigidity in the circumferential direction. In a tire having a poor uniformity, vibrations such as a shake and a roughness are generated. In such a tire, a silence and a ride comfort are poor.
It is an object of the present invention to provide a pneumatic tire which is excellent in a silence and a ride comfort.